Modern Doppler radars utilize a single receiver channel and frequency tracker to be time shared between the Doppler shifted returns. For Doppler velocity tracking to approximately 750 knots, low cost standardized components exist to track the Doppler shifted signals of the fore beams and then, a few milliseconds later, slew and track the negative Doppler signals of the aft beam. Additionally, low speed applications require a Doppler passband only of about .+-.12 KHz centered around an intermediate frequency of approximately 40 KHz. This allows a power supply inverter frequency to be designed above the Doppler passband, but less than a practical upper limit 55 KHz. (This insures that power supply ripple frequencies and harmonics are out of the Doppler passband and do not cause spurious Doppler signals).
For a Doppler application where tracking is 2000 knots, the high slew rate required to go from positive to negative shifted Doppler signal precludes the use of standardized components. Furthermore, the intermediate frequency range of the receiver unit must be increased to 40 KHz .+-.25 KHz. This requires a power supply inverter frequency of greater than 70 KHz which is impractical for a high efficiency switching supply.